Traditional granular surfaced roofing shingles are well known. Such shingles generally have been made with a substrate which may constitute organic fibre saturated with bitumen, or chopped glass fibre bonded with urea-formaldehyde or other types of resins. Typically, the substrate is first coated with a mixture of bitumen and filler such as limestone, or similar inorganic fillers. The coated substrate then is covered with mineral granules which may be coloured to give aesthetic appeal to the face of the shingles. A parting agent is applied to the back of the substrate so that the packaged shingles do not stick together. In some cases, a bitumenous sealant is also placed on the granulated side of the shingles to enhance adhesion to the back of covering shingles in the final applied configuration. Typically on conventional shingles, such bitumenous sealant is a stitched or interrupted line of sealant positioned generally adjacent the horizontal midpoint of the shingle, (i.e., in a tabbed shingle, above any cut-out between tabs).
Many variations of this typical shingle system have been disclosed. Fasold Canadian patent 644,823 discloses a release tape in contact with the adhesive strip of an adjacent shingle in a shingle stack of sequentially reversed shingles whereby the release tape would not contact the adhesive when the shingles are installed. Kirschbraun Canadian patent 403,975 discloses a fugitive release material, such as salt, to inhibit premature sealing of the adhesive in stacked shingles. Burtch Canadian patent 900,136 discloses a sinuous adhesive pattern applied by hand during the installation of a roof system. Corbin Canadian patent 900,136 discloses an adhesive strip on the underside of a shingle, to adhere the head of the shingle to the roof deck. Buck U.S. Pat. No. 4,856,251 discloses a self-gauging partial two-ply shingle with a standard stitch adhesive strip at the tab and a solid adhesive strip located at the rear edge of the shingle.
One typical shingle is a “three tab” shingle, in which the shingle sheet has two full cut-outs and half cut-outs at each side edge defining three tabs or flaps which, on a finished roof, resemble individual shingles. Other shingles may have multiple tabs, or no tabs (i.e., slab shingles). Still other common shingles are laminated or overlay shingles which may not have cut-outs.
Again, typically a bead or strip of temperature sensitive adhesive or sealant such as a bitumenous compound, is applied to either the upper or the lower surface of the shingle, in a location such that the bead or strip is located beneath the butt end of the flaps of an installed overlying shingle. Under conditions of heat, the bitumenous compound adheres the butt edge of a flap to the surface of an underlying shingle. This line of adhesive is “stitched” leaving intermittent gaps, to permit drainage of any moisture which may condense or be driven under the shingle, either at a lateral joint between adjacent shingles, at the tab cut-outs or the lateral edge of a roofing.
Certain building codes, such as the International Residential Building Code, the South Florida Building Code, and specifically the Dade County Building Code have raised the performance requirements of roofing products. In the case of Dade County, the code requires any system of bitumenous roofing shingles not only to resist hurricane wind forces as high as 110 mph, but also resist such wind driven rain. Similar codes are being adopted by several States in the USA that are prone to high wind and rain damage. These are generally located in the coastal regions of the USA.
Current shingles have a built-in weakness, namely the shingle tab adhesive compound is applied in a “stitch” or intermittent pattern (as opposed to a continuous strip of adhesive along the length of the shingle). Consequently, sufficiently high velocity wind and rain can enter the gaps between the adhesive elements and can lift the overlaying second layer of shingle tabs. If the forces of wind and rain are sufficiently strong, or if the bond between the adhesive “elements” adhering to the shingle tabs are weak, the tabs will lift, and sometimes blow off. If rain is driven under the overlying shingles or through the stitch gaps and penetrates between the shingles sufficiently to exceed the “headlap”, it overflows the top or head edge of the underlying shingles and spills onto the roof deck. Headlap is commonly known as the shortest distance from the horizontal top edge of a shingle to the nearest exposed area of that shingle. In conventional tab shingles, the headlap distance from the apex of a cut-out to the top edge of a shingle is normally 2″.
When shingle damage is done, rainwater can easily damage the wooden deck and subsequently the interior of the building. To avoid such potential damage, the South Florida Building Code has issued a mandatory roofing shingle application procedure in which two layers of 30# bitumen impregnated or suitable “underlayment” membranes are nailed down with specific nails/metal washers in a very defined manner. The factory made roofing shingles are nailed upon this underlayment.
Industry relies on the underlayment to provide the protection against wind driven rain. Thus, should the shingle sealant tabs break loose from the adhesive, the barrier of the underlayment (if nailed per the code) prevents further damage to the roof.
The present invention provides a continuous band of sealant along the length of the shingles, parallel to the long edges and about twice the exposed width (as specified by the manufacturer) of the shingle from the lower edge. This sealant strip is a physical barrier to the upward flow of water.
Contrary to the shingle and underlayment system required under the South Florida Building Code, it is anticipated that in the present invention the sealed shingles themselves will provide adequate resistance to the wind driven rain, without the necessity of underlayment.
In addition, the present invention can be utilized to increase the exposed area of the same shingle. This is an economic advantage to the manufacturer as well as to the roofing contractor and consequently the owner of the roof.
The rationale in favour of larger exposure area is as follows:    The current ASTM D225-01, D3462-02, CSA 123-1, CSA 123-51, CSA 123-5, European EN544, prescribe that the size of the shingle and specifically the width/depth of the shingle (shorter dimension) must be such that when shingles are nailed on the roof, there will be a minimum of 2″ (51 mm) of headlap (see FIG. 1).
The fundamental intent of this mandatory requirement is based on the premise that if wind-driven rain were to travel upward on the underlying shingle from the exposed area, then, in order to prevent this forced rain water from going over the head or top edge of the underlying shingle, it would have to travel a minimum distance of 2″ (51 mm). This is considered adequate under most weather conditions.
This particular requirement is critical for overlaying shingles that have “cut-outs” that allow forced rainwater to travel towards the head edge of the underlying shingle. Joints between shingles are also considered as entry points, especially when the width of the cut-out is wider, such as ½″ or more. In such a case, this requirement is critical as the volume of rainwater is greater in a wider cut-out as opposed to narrower (than ½″) cut-outs.
The general industry accepted formula for a shingle width (depth) is:2× exposure+2″ (51 mm) headlap,where “exposure” is the portion of the shingle not covered by an overlying shingle, (which is often the same as the length of the cut-outs in a tabbed shingle).
Part of the above referenced 2″ (51 mm) headlap requirement becomes unnecessary if the upward travel of the wind forced rainwater is blocked off by a continuous strip (bead or band) of factory applied sealant on the face of the shingle.
Thus, for example, when a band of sealant is applied in the area about two times the “exposure” from the butt edge of a shingle, it seals the path of potential rainwater entry. Consequently, the traditional 2″ headlap is unnecessary. This excess shingle material of the headlap can simply be eliminated, resulting in a reduction in shingle material for the same coverage. Alternatively, if the same physical size of shingle is retained, the headlap can be reduced and the bead of sealant can be located near the top edge of the shingle. This provides a wider exposed surface for each shingle. Consequently, the larger exposure means a fewer number of shingles would be required to cover a unit area.